KR100273198B1 - METHOD OF PRODUCING HIGH PURITY Si POWDER FROM SiO2 USING SELF-PROPAGATING HIGH TEMPERATURE SYNTHESIS - Google Patents

Abstract

PURPOSE: A method of producing high purity Si powder from SiO2 using self-propagating high temperature synthesis is provided. Si powder produced by this method has a high purity of over 99.988%, and this method is economical and less energy consumptive. CONSTITUTION: The method comprises the steps of (S1) mixing SiO2 with Mg at a ratio of 1 to 2-2.5, wherein the SiO2 has a particle size of 140μm and a purity over 99.74%, and Mg has a particle size distribution of 10 to 100μm; (S2) forming the mixture in the shape of pellet by compressing the mixture at 4 to 14 ton; (S3) charging the pellet into self propagating reactor; (S4) firing the pellet in the reactor under Ar gas atmosphere or vacuum condition; (S5) withdrawing combustion product from the self propagating reactor; (S6) leaching the combustion product with 10-50% HCl or H2SO4 for 1-3 hours; (S7) filtrating leached residuals; (S8) washing filtrated Si powder followed by drying in a temperature range of 60 to 90deg.C.

Description

Process for producing high purity silicon powder from silicon oxide using self-burning reaction

The present invention relates to a method for producing silicon (Si) powder from silicon oxide (SiO ₂ ) powder by using a self-propagating high-temperature synthesis (hereinafter referred to as SHS), in particular silicon oxide ( SiO ₂ ) and magnesium (Mg) mixed in a constant molar ratio to prepare a mixed powder of silicon (Si) -magnesium oxide (MgO) using SHS and to produce a high-purity silicon (Si) powder through a leaching process It is about.

In general, silicon (Si) is widely present in rocks in the form of compounds such as oxides and silicates, and is an element that exists in large quantities after oxygen on the earth. The ore used for smelting is high quality silica (SiO ₂ ). Metallic silicon (Si) is dark grayish silver, hardened and brittle, and its compressive strength is about 100 MPa. Metallic silicon (Si) is very stable chemically and therefore does not interact with almost all materials at room temperature. High purity silicon (Si) is a semiconductor.

Metallic silicon (Si) having such physical properties is added for deoxidation purposes in steelmaking, steelmaking or nonferrous metallurgy, and may be added as an alloying element for increasing the hardness of the alloy. For example, it is mainly added as a component element of aluminum alloy. In addition, metal silicon (Si) is added as a component element of the silicon resin, the silicon steel sheet, and the cast iron. Metal silicon (Si) is also used as a high purity silicon (Si) raw material for semiconductors. Most of high purity silicon (Si) is used as a semiconductor device by single crystallization, and is also used as an amorphous or polycrystalline form. Semiconductor silicon (Si) is used in transistors, integrated circuits (ICs), photodiodes, photovoltaic cells, and photoconductive devices.

To date, pure silicon (Si) is produced by carbon reduction in electric furnaces. High purity silicon (Si) is prepared by converting industrial metal silicon (Si) into trichlorosilane (SiHCl ₃ ) or monosilane (SiH ₄ ) and purifying it, followed by hydrogen reduction or pyrolysis. Alternatively, silicon tetrachloride (SiCl ₄ ) may be reduced with zinc or hydrogen. However, in the case of producing silicon (Si) through such a process, not only the manufacturing facilities and manufacturing processes are complicated, but also a large amount of energy must be supplied.

The present invention has been made to solve the conventional problems as described above, an object of the present invention is to mix silicon oxide (SiO ₂ ) and magnesium (Mg) in a constant molar ratio in the self-combustion reaction method and silicon (SHS) After preparing a mixed powder of Si) -magnesium oxide (MgO) and leaching with about 10 to 50% hydrochloric acid (HCl) or sulfuric acid (H ₂ SO ₄ ) to remove magnesium oxide (MgO), Si) to provide a method for producing a powder.

1 is a manufacturing process diagram of a high purity silicon (Si) powder according to the present invention,

2 is a schematic representation of the configuration of a self-burning reactor used to carry out the present invention;

Figure 3 is a graph showing the X-ray diffraction results of the reaction product obtained by the self-burn reaction of a powder mixed with silicon oxide (SiO ₂ ) and magnesium (Mg) in a molar ratio of 1: 2.0 according to a preferred embodiment of the present invention, And

FIG. 4 shows the results of X-ray diffraction after leaching the reaction product obtained by self-combustion of a powder mixed with silicon oxide (SiO ₂ ) and magnesium (Mg) in a molar ratio of 1: 2.0 according to a preferred embodiment of the present invention. The graph shown.

<Explanation of symbols for main parts of drawing>

12 green pellet 14 thermocouple

16: data collector 20: computer

22 tungsten (W) filament 24 power source

26: heat-resistant glass 28: vacuum pump

30: inert gas source 32: vent

34 cooling device 100 self-burning reactor

102: reactor chamber

In order to achieve the above object, the present invention,

Mixing silicon oxide (SiO ₂ ) and magnesium (Mg) at a constant ratio (S1);

Molding the mixture formed in the step (S1) into pellets (S2);

Charging said pellets into a self-combustion reactor (S3);

Combusting the pellets in the self-burning reactor (S4);

Taking out the combustion product made in the step (S4) from the self-combustion reactor (S5);

Leaching the combustion product (S6);

Filtering the leachate leaching in step S6 (S7);

Washing the silicon (Si) powder filtered in the step S7 (S8); And

It provides a method for producing a high purity silicon powder comprising the step (S9) of drying the silicon (Si) powder washed in the step (S8).

The silicon oxide (SiO ₂ ) and the magnesium (Mg) is the following reaction formula

SiO ₂ + 2Mg → Si + 2MgO is mixed to satisfy.

Preferably, the mixing ratio of the silicon oxide (SiO ₂ ) and the magnesium (Mg) is 1: (2 to 2.5).

The self burning reactor is maintained in a vacuum atmosphere or argon (Ar) gas atmosphere.

In the above (S6), the combustion product is leached over 1 to 3 hours using hydrochloric acid (HCl) or sulfuric acid (H ₂ SO ₄ ) diluted to 10 to 50%. In the above (S9), the silicon (Si) powder is sufficiently dried in a dryer maintained at a temperature of 60 to 70 ° C.

As mentioned above, in the method for producing high purity silicon (Si) powder according to the present invention, a mixture of silicon (Si) -magnesium oxide (MgO) from silicon oxide (SiO ₂ ) and magnesium (MgO) using SHS After the powder is prepared, it is leached with hydrochloric acid (HCl) or sulfuric acid (H ₂ SO ₄ ) diluted to 10 to 50% to prepare high-purity silicon (Si) powder.

Hereinafter, a process of manufacturing high purity silicon (Si) powder according to the present invention with reference to the accompanying drawings in more detail.

First, FIG. 2 is a diagram schematically showing the configuration of a self-burning reactor used to carry out the present invention. Referring to FIG. 2, the self-burning reactor 100 mainly consists of the reactor chamber 102 and its peripheral devices. The self-burning reactor 100 may have any structure as long as it can create a vacuum or inert gas atmosphere in the reactor chamber 102 and ignite the specimen located in the reactor chamber 102.

A green pellet 12 made of silicon oxide (SiO ₂ ) and magnesium (Mg) is positioned in the center of the reactor chamber 102 of the self-combustion reactor 100. One side of the green pellet 12 is equipped with a thermocouple 14 for measuring the temperature of the green pellet 12 to be burned. Thermocouple 14 is electrically connected to computer 20 via data collector 16.

Within the reactor chamber 102, tungsten filaments 22 for igniting the green pellets 12 are located just above the green pellets 12. Tungsten filament 22 receives current from a power source 24 located outside the reactor chamber 102. On one side wall of the reactor chamber 102 is a heat-resistant glass 26 of a disc shape that can be opened and closed. The heat-resistant glass 26 performs the inlet and outlet of the green pellet 12 while opening and closing as needed, and allows the operator to check the combustion state of the green pellet 12 with the naked eye through the heat-resistant glass 26. .

At the bottom of the reactor chamber 102 is connected a vacuum hose 29 for establishing a vacuum in the reactor chamber 102. The vacuum hose 29 extends to a vacuum pump 28 located outside the reactor chamber 102. The vacuum pump 28 draws air in the reactor chamber 102 as needed to create a vacuum. In addition, an inert gas supply hose 31 for introducing an inert gas into the reactor chamber 102 is connected to a lower end of the reactor chamber 102. The inert gas supply hose 31 extends to an inert gas supply source 30 located outside the reactor chamber 102. Inert gas source 30 provides inert gas, such as hydrogen (H ₂ ) or argon (Ar), into reactor chamber 102 as needed.

In addition, the vent 32 formed on one side of the lower end of the reactor chamber 102 maintains a constant pressure in the reactor chamber 102 or discharges the pressure in the reactor chamber 102 to the outside when the heat-resistant glass 26 is opened. Let's do it. Cooling devices 34 for maintaining a constant temperature in the reactor chamber 102 are installed in the upper and lower portions of the reactor chamber 102. Above the outer side of the reactor chamber 102, a vacuum instrument panel 36 is provided for notifying the vacuum state formed in the reactor chamber 102.

On the other hand, Figure 1 is a manufacturing process of the high purity silicon (Si) powder according to the present invention. A process for producing high purity silicon (Si) powder using a self-burning reactor 100 having the configuration as described above with reference to FIGS. 1 and 2 will be described.

The present invention mixes silicon oxide (SiO ₂ ) and magnesium (Mg) in a constant molar ratio to obtain a composite of silicon (Si) -magnesium oxide (MgO) by SHS under an appropriate reaction atmosphere, which is about 10 to 50% It is a method of obtaining high purity silicon (Si) by removing magnesium oxide (MgO) by leaching with hydrochloric acid (HCl) or sulfuric acid (H ₂ SO ₄ ). In general, the SHS used in the present invention is a self-combustion reaction method in which a chemical reaction between a solid and a solid is an exothermic reaction and synthesizes a material using its own heat of chemical reaction after ignition of the material without supplying energy from the outside.

As the raw material powder used in the present invention, silicon oxide (SiO ₂ ) having a particle size of 140 μm and magnesium (Mg) having a particle size of 10 to 100 μm are employed. At this time, the purity of the silicon oxide (SiO ₂ ) of the raw material powder is closely related to the purity of the high purity silicon (Si) powder to be obtained in the present invention. That is, as the purity of silicon oxide (SiO ₂ ) is increased, the purity of silicon (Si) is increased. Preferably, the purity of silicon oxide (SiO ₂ ) is at least 98.74%.

After provided the silicon oxide (SiO ₂₎ and magnesium (Mg) is to be mixed uniformly in the reaction scheme a silicon oxide (SiO ₂₎ and magnesium (Mg) as (Ⅰ) at a predetermined composition ratio.

SiO ₂ + 2 Mg → Si + 2 MgO ―――― (I)

Preferably, silicon oxide (SiO ₂ ) and magnesium (Mg) are uniformly mixed in a molar ratio of 1: (2 to 2.5). Next, the mixture of silicon oxide (SiO ₂ ) and magnesium (Mg) is compressed by applying a predetermined molding pressure. Preferably, it compresses by applying molding pressure of 4-14t. This is because, when a molding pressure of 4t or less is applied, the pellet is easily broken due to the low pressure, and when the molding pressure of 14t or more is applied, the pellet does not ignite well.

After compacting the mixture of silicon oxide (SiO ₂ ) and magnesium (Mg), the heat-resistant glass 26 of the self-combustion reactor 100 is opened and a green pellet (12) consisting of silicon oxide (SiO ₂ ) and magnesium (Mg) ) Into the reactor chamber 102. That is, the green pellet 12 is located at the center in the reactor chamber 102. Under this condition, after closing the heat-resistant glass 26, the vacuum pump 28 is operated to create a vacuum in the reactor chamber 102, or the inert gas source 30 is operated to inert gas, into the reactor chamber 102, Preferably argon (Ar) gas is introduced. Under this condition, a current is applied from the power supply source 24 to the tungsten filament 22 to ignite and burn the green pellet 12.

Thus, after obtaining silicon (Si) and magnesium oxide (MgO) from the green pellet 12 consisting of silicon oxide (SiO ₂ ) and magnesium (Mg), about 10 to 50% of the reaction formula (II) Leaching with hydrochloric acid (HCl) to remove magnesium oxide (MgO) to obtain high purity silicon (Si).

Si + 2MgO + (HCl) (L) → Si ↓ + (2MgO + HCl) (L) ---―- (II)

At this time, the temperature is maintained at about 50 ~ 70 ℃, the reaction is carried out for 1 to 3 hours.

Preferably, 10 to 50% of hydrochloric acid (H ₂ SO ₄ ) may be used instead of hydrochloric acid (HCL).

The precipitated silicon (Si) powder is recovered using a filter paper, washed several times, and dried in a drier maintained at about 70 ° C. for about 18 hours to obtain pure silicon (Si) powder. The finally produced silicon (Si) shows a high purity of 99.988% or more because impurities are volatilized during the combustion process.

Hereinafter, a preferred embodiment of the present invention will be briefly described.

Example

As a raw material powder, silicon oxide (SiO ₂ ) (manufactured by Japan Pure Chemicals Co., Ltd.) and magnesium (Mg) were added to a ball mill at a molar ratio of 1: 2 to 2.5, respectively, and mixed for 2 hours or more. Next, the mixed powder is subjected to a pressure of 4 to 14 tons to form pellets having a diameter of 20 mm and a height of 15 to 20 mm. The pellets thus formed are dried in a dryer maintained at about 70 ° C. and then ignited and burned in an inert gas atmosphere, preferably in an argon (Ar) gas atmosphere, in a self-combustion reactor. The reaction product produced by ignition and burning the molded pellet was leached for 1 to 3 hours using about 10 to 50% of hydrochloric acid (HCl) or sulfuric acid (H ₂ SO ₄ ) solution, and then precipitated using a filter paper. Recovered silicon (Si) was recovered. Then, the silicon (Si) is washed three to five times and dried sufficiently in a drier maintained at a temperature of about 60 to 70 ° C. to produce pure silicon (Si) powder, followed by X-ray diffraction (X-Ray Diffraction). Analyze the crystal structure using

Figure 3 is a graph showing the X-ray diffraction results of the reaction product obtained by the self-burn reaction of a powder mixed with silicon oxide (SiO ₂ ) and magnesium (Mg) in a molar ratio of 1: 2.0 according to a preferred embodiment of the present invention . FIG. 4 shows the results of X-ray diffraction after leaching the reaction product obtained by self-combustion of a powder mixed with silicon oxide (SiO ₂ ) and magnesium (Mg) in a molar ratio of 1: 2.0 according to a preferred embodiment of the present invention. The graph shown.

Referring to FIGS. 3 and 4, it can be seen that magnesium oxide (MgO) as shown in FIG. 3 is removed by leaching, so that only silicon (Si) is present as a final product. In addition, the final product was measured by atomic absorption spectrometer, it was confirmed that the high purity powder of 99.988% or more.

As mentioned above, in the method for producing silicon (Si) powder according to the present invention, magnesium oxide (MgO) obtained as a by-product after reducing silicon oxide (SiO ₂ ) powder using magnesium (Mg) as a reducing agent Is leached with about 10-50% hydrochloric acid (HCl) or sulfuric acid (H ₂ SO ₄ ) to prepare a silicon (Si) powder. Therefore, the high temperature reactor required by the conventional method for producing silicon (Si) powder becomes unnecessary, and the manufacturing process is simplified. In addition, since the combustion reaction of the reactants proceeds automatically by the self-heating amount, high energy efficiency and high exothermic temperature cause volatilization of impurities to obtain high-purity silicon (Si) powder. In addition, since the reaction itself starts from an oxide, silicon (Si) can be directly synthesized without the need for smelting, and can be synthesized in the air.

Although described above with reference to a preferred embodiment of the present invention, those skilled in the art will be variously modified and changed within the scope of the invention without departing from the spirit and scope of the invention described in the claims below. I can understand that you can.

Claims (8)

Mixing silicon oxide (SiO ₂ ) and magnesium (Mg) at a constant ratio (S1); Molding the mixture formed in the step (S1) into pellets (S2); Charging said pellets into a self-combustion reactor (S3); Combusting the pellets in the self-burning reactor (S4); Taking out the combustion product made in the step (S4) from the self-combustion reactor (S5); Leaching the combustion product (S6); Filtering the leachate leaching in step S6 (S7); Washing the silicon (Si) powder filtered in the step S7 (S8); And Method for producing a high-purity silicon powder comprising the step (S9) of drying the silicon (Si) powder washed in the step (S8). The method of claim 1, wherein the silicon oxide (SiO ₂ ) and the magnesium (Mg) is the following reaction scheme SiO ₂ + 2Mg → Si + 2MgO And a mixture ratio of the silicon oxide (SiO ₂ ) and the magnesium (Mg) is 1: (2 to 2.5). The method of claim 1, wherein the silicon oxide (SiO ₂ ) has a particle size of 140 μm and a purity of 99.74% or more, and the magnesium (Mg) has a particle size distribution of 10 to 100 μm. . The method of claim 1, wherein in the step (S2), the mixture is compressed by applying a molding pressure of 4 to 14 tons to form the pellets. The method for producing high purity silicon powder according to claim 1, wherein a vacuum atmosphere is formed in the self-combustion reactor. The method of claim 1, wherein argon (Ar) gas atmosphere is formed in the self-combustion reactor chamber. The method of claim 1, wherein in (S6), leaching the combustion product for 1 to 3 hours using hydrochloric acid (HCl) or sulfuric acid (H ₂ SO ₄ ) diluted to 10-50%. Method for producing high purity silicon powder. The method for producing high purity silicon powder according to claim 1, wherein in step S9, the silicon (Si) powder is sufficiently dried in a dryer maintained at a temperature of 60 to 70 ° C.